mirror of
https://github.com/Unidata/netcdf-c.git
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1031 lines
35 KiB
C
1031 lines
35 KiB
C
/*
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-------------------------------------------------------------------------------
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lookup3.c, by Bob Jenkins, May 2006, Public Domain.
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Original: http://burtleburtle.net/bob/c/lookup3.c
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Modified by Russ Rew for adaption in netCDF.
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- Make use of Paul Hsieh's pstdint.h, if stdint.h not available.
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- Declare unused functions static to keep global namespace clean.
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- Provide function hash_fast() that uses either hashlittle() or
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hashbig(), depending on endianness.
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- Because portability is more important than speed for netCDF use,
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we define VALGRIND to skip "#ifndef VALGRIND" code, so reads of
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strings don't access extra bytes after end of string. This may
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slow it down enough to justify a simpler hash, but blame me, not
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original author!
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These are functions for producing 32-bit hashes for hash table lookup.
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hashword(), hashlittle(), hashlittle2(), hashbig(), mix(), and final()
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are externally useful functions. Routines to test the hash are included
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if SELF_TEST is defined. You can use this free for any purpose. It's in
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the public domain. It has no warranty.
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You probably want to use hashlittle(). hashlittle() and hashbig()
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hash byte arrays. hashlittle() is is faster than hashbig() on
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little-endian machines. Intel and AMD are little-endian machines.
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On second thought, you probably want hashlittle2(), which is identical to
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hashlittle() except it returns two 32-bit hashes for the price of one.
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You could implement hashbig2() if you wanted but I haven't bothered here.
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If you want to find a hash of, say, exactly 7 integers, do
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a = i1; b = i2; c = i3;
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mix(a,b,c);
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a += i4; b += i5; c += i6;
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mix(a,b,c);
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a += i7;
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final(a,b,c);
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then use c as the hash value. If you have a variable length array of
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4-byte integers to hash, use hashword(). If you have a byte array (like
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a character string), use hashlittle(). If you have several byte arrays, or
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a mix of things, see the comments above hashlittle().
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Why is this so big? I read 12 bytes at a time into 3 4-byte integers,
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then mix those integers. This is fast (you can do a lot more thorough
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mixing with 12*3 instructions on 3 integers than you can with 3 instructions
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on 1 byte), but shoehorning those bytes into integers efficiently is messy.
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-------------------------------------------------------------------------------
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*/
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/* #define SELF_TEST 1 */
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#if HAVE_CONFIG_H
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#include <config.h>
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#endif
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#include <stdio.h> /* defines printf for tests */
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#include <time.h> /* defines time_t for timings in the test */
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#ifndef HAVE_STDINT_H
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# include "pstdint.h" /* attempts to define uint32_t etc portably */
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#else
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# include <stdint.h>
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#endif /* HAVE_STDINT_H */
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#ifdef HAVE_SYS_PARAM_H
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#include <sys/param.h> /* attempt to define endianness */
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#endif /* HAVE_SYS_PARAM_H */
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#ifdef linux
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# include <endian.h> /* attempt to define endianness */
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#endif
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#define VALGRIND /* added by Russ Rew, for portability over speed */
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#ifndef WORDS_BIGENDIAN /* from config.h */
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#define HASH_LITTLE_ENDIAN 1
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#define HASH_BIG_ENDIAN 0
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#else
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#define HASH_LITTLE_ENDIAN 0
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#define HASH_BIG_ENDIAN 1
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#endif
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#define hashsize(n) ((uint32_t)1<<(n))
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#define hashmask(n) (hashsize(n)-1)
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#define rot(x,k) (((x)<<(k)) | ((x)>>(32-(k))))
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/*
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-------------------------------------------------------------------------------
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mix -- mix 3 32-bit values reversibly.
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This is reversible, so any information in (a,b,c) before mix() is
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still in (a,b,c) after mix().
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If four pairs of (a,b,c) inputs are run through mix(), or through
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mix() in reverse, there are at least 32 bits of the output that
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are sometimes the same for one pair and different for another pair.
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This was tested for:
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* pairs that differed by one bit, by two bits, in any combination
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of top bits of (a,b,c), or in any combination of bottom bits of
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(a,b,c).
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* "differ" is defined as +, -, ^, or ~^. For + and -, I transformed
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the output delta to a Gray code (a^(a>>1)) so a string of 1's (as
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is commonly produced by subtraction) look like a single 1-bit
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difference.
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* the base values were pseudorandom, all zero but one bit set, or
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all zero plus a counter that starts at zero.
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Some k values for my "a-=c; a^=rot(c,k); c+=b;" arrangement that
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satisfy this are
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4 6 8 16 19 4
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9 15 3 18 27 15
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14 9 3 7 17 3
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Well, "9 15 3 18 27 15" didn't quite get 32 bits diffing
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for "differ" defined as + with a one-bit base and a two-bit delta. I
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used http://burtleburtle.net/bob/hash/avalanche.html to choose
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the operations, constants, and arrangements of the variables.
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This does not achieve avalanche. There are input bits of (a,b,c)
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that fail to affect some output bits of (a,b,c), especially of a. The
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most thoroughly mixed value is c, but it doesn't really even achieve
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avalanche in c.
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This allows some parallelism. Read-after-writes are good at doubling
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the number of bits affected, so the goal of mixing pulls in the opposite
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direction as the goal of parallelism. I did what I could. Rotates
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seem to cost as much as shifts on every machine I could lay my hands
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on, and rotates are much kinder to the top and bottom bits, so I used
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rotates.
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-------------------------------------------------------------------------------
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*/
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#define mix(a,b,c) \
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{ \
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a -= c; a ^= rot(c, 4); c += b; \
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b -= a; b ^= rot(a, 6); a += c; \
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c -= b; c ^= rot(b, 8); b += a; \
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a -= c; a ^= rot(c,16); c += b; \
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b -= a; b ^= rot(a,19); a += c; \
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c -= b; c ^= rot(b, 4); b += a; \
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}
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/*
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-------------------------------------------------------------------------------
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final -- final mixing of 3 32-bit values (a,b,c) into c
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Pairs of (a,b,c) values differing in only a few bits will usually
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produce values of c that look totally different. This was tested for
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* pairs that differed by one bit, by two bits, in any combination
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of top bits of (a,b,c), or in any combination of bottom bits of
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(a,b,c).
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* "differ" is defined as +, -, ^, or ~^. For + and -, I transformed
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the output delta to a Gray code (a^(a>>1)) so a string of 1's (as
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is commonly produced by subtraction) look like a single 1-bit
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difference.
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* the base values were pseudorandom, all zero but one bit set, or
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all zero plus a counter that starts at zero.
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These constants passed:
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14 11 25 16 4 14 24
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12 14 25 16 4 14 24
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and these came close:
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4 8 15 26 3 22 24
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10 8 15 26 3 22 24
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11 8 15 26 3 22 24
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-------------------------------------------------------------------------------
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*/
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#define final(a,b,c) \
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{ \
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c ^= b; c -= rot(b,14); \
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a ^= c; a -= rot(c,11); \
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b ^= a; b -= rot(a,25); \
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c ^= b; c -= rot(b,16); \
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a ^= c; a -= rot(c,4); \
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b ^= a; b -= rot(a,14); \
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c ^= b; c -= rot(b,24); \
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}
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/*
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--------------------------------------------------------------------
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This works on all machines. To be useful, it requires
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-- that the key be an array of uint32_t's, and
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-- that the length be the number of uint32_t's in the key
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The function hashword() is identical to hashlittle() on little-endian
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machines, and identical to hashbig() on big-endian machines,
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except that the length has to be measured in uint32_ts rather than in
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bytes. hashlittle() is more complicated than hashword() only because
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hashlittle() has to dance around fitting the key bytes into registers.
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--------------------------------------------------------------------
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*/
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#ifdef SELF_TEST
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static
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uint32_t hashword(
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const uint32_t *k, /* the key, an array of uint32_t values */
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size_t length, /* the length of the key, in uint32_ts */
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uint32_t initval) /* the previous hash, or an arbitrary value */
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{
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uint32_t a,b,c;
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/* Set up the internal state */
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a = b = c = 0xdeadbeef + (((uint32_t)length)<<2) + initval;
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/*------------------------------------------------- handle most of the key */
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while (length > 3)
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{
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a += k[0];
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b += k[1];
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c += k[2];
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mix(a,b,c);
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length -= 3;
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k += 3;
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}
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/*------------------------------------------- handle the last 3 uint32_t's */
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switch(length) /* all the case statements fall through */
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{
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case 3 : c+=k[2];
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case 2 : b+=k[1];
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case 1 : a+=k[0];
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final(a,b,c);
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case 0: /* case 0: nothing left to add */
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break;
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}
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/*------------------------------------------------------ report the result */
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return c;
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}
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/*
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--------------------------------------------------------------------
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hashword2() -- same as hashword(), but take two seeds and return two
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32-bit values. pc and pb must both be nonnull, and *pc and *pb must
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both be initialized with seeds. If you pass in (*pb)==0, the output
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(*pc) will be the same as the return value from hashword().
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--------------------------------------------------------------------
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*/
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static
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void hashword2 (
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const uint32_t *k, /* the key, an array of uint32_t values */
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size_t length, /* the length of the key, in uint32_ts */
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uint32_t *pc, /* IN: seed OUT: primary hash value */
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uint32_t *pb) /* IN: more seed OUT: secondary hash value */
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{
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uint32_t a,b,c;
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/* Set up the internal state */
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a = b = c = 0xdeadbeef + ((uint32_t)(length<<2)) + *pc;
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c += *pb;
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/*------------------------------------------------- handle most of the key */
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while (length > 3)
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{
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a += k[0];
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b += k[1];
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c += k[2];
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mix(a,b,c);
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length -= 3;
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k += 3;
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}
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/*------------------------------------------- handle the last 3 uint32_t's */
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switch(length) /* all the case statements fall through */
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{
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case 3 : c+=k[2];
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case 2 : b+=k[1];
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case 1 : a+=k[0];
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final(a,b,c);
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case 0: /* case 0: nothing left to add */
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break;
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}
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/*------------------------------------------------------ report the result */
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*pc=c; *pb=b;
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}
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/*
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* hashlittle2: return 2 32-bit hash values
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*
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* This is identical to hashlittle(), except it returns two 32-bit hash
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* values instead of just one. This is good enough for hash table
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* lookup with 2^^64 buckets, or if you want a second hash if you're not
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* happy with the first, or if you want a probably-unique 64-bit ID for
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* the key. *pc is better mixed than *pb, so use *pc first. If you want
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* a 64-bit value do something like "*pc + (((uint64_t)*pb)<<32)".
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*/
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static void
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hashlittle2(
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const void *key, /* the key to hash */
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size_t length, /* length of the key */
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uint32_t *pc, /* IN: primary initval, OUT: primary hash */
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uint32_t *pb) /* IN: secondary initval, OUT: secondary hash */
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{
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uint32_t a,b,c; /* internal state */
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union { const void *ptr; size_t i; } u; /* needed for Mac Powerbook G4 */
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/* Set up the internal state */
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a = b = c = 0xdeadbeef + ((uint32_t)length) + *pc;
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c += *pb;
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u.ptr = key;
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if (HASH_LITTLE_ENDIAN && ((u.i & 0x3) == 0)) {
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const uint32_t *k = (const uint32_t *)key; /* read 32-bit chunks */
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const uint8_t *k8;
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/*------ all but last block: aligned reads and affect 32 bits of (a,b,c) */
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while (length > 12)
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{
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a += k[0];
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b += k[1];
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c += k[2];
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mix(a,b,c);
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length -= 12;
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k += 3;
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}
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/*----------------------------- handle the last (probably partial) block */
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/*
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* "k[2]&0xffffff" actually reads beyond the end of the string, but
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* then masks off the part it's not allowed to read. Because the
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* string is aligned, the masked-off tail is in the same word as the
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* rest of the string. Every machine with memory protection I've seen
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* does it on word boundaries, so is OK with this. But VALGRIND will
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* still catch it and complain. The masking trick does make the hash
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* noticeably faster for short strings (like English words).
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*/
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#ifndef VALGRIND
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switch(length)
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{
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case 12: c+=k[2]; b+=k[1]; a+=k[0]; break;
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case 11: c+=k[2]&0xffffff; b+=k[1]; a+=k[0]; break;
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case 10: c+=k[2]&0xffff; b+=k[1]; a+=k[0]; break;
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case 9 : c+=k[2]&0xff; b+=k[1]; a+=k[0]; break;
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case 8 : b+=k[1]; a+=k[0]; break;
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case 7 : b+=k[1]&0xffffff; a+=k[0]; break;
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case 6 : b+=k[1]&0xffff; a+=k[0]; break;
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case 5 : b+=k[1]&0xff; a+=k[0]; break;
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case 4 : a+=k[0]; break;
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case 3 : a+=k[0]&0xffffff; break;
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case 2 : a+=k[0]&0xffff; break;
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case 1 : a+=k[0]&0xff; break;
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case 0 : *pc=c; *pb=b; return; /* zero length strings require no mixing */
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}
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#else /* make valgrind happy */
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k8 = (const uint8_t *)k;
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switch(length)
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{
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case 12: c+=k[2]; b+=k[1]; a+=k[0]; break;
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case 11: c+=((uint32_t)k8[10])<<16; /* fall through */
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case 10: c+=((uint32_t)k8[9])<<8; /* fall through */
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case 9 : c+=k8[8]; /* fall through */
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case 8 : b+=k[1]; a+=k[0]; break;
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case 7 : b+=((uint32_t)k8[6])<<16; /* fall through */
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case 6 : b+=((uint32_t)k8[5])<<8; /* fall through */
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case 5 : b+=k8[4]; /* fall through */
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case 4 : a+=k[0]; break;
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case 3 : a+=((uint32_t)k8[2])<<16; /* fall through */
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case 2 : a+=((uint32_t)k8[1])<<8; /* fall through */
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case 1 : a+=k8[0]; break;
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case 0 : *pc=c; *pb=b; return; /* zero length strings require no mixing */
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}
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#endif /* !valgrind */
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} else if (HASH_LITTLE_ENDIAN && ((u.i & 0x1) == 0)) {
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const uint16_t *k = (const uint16_t *)key; /* read 16-bit chunks */
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const uint8_t *k8;
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/*--------------- all but last block: aligned reads and different mixing */
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while (length > 12)
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{
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a += k[0] + (((uint32_t)k[1])<<16);
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b += k[2] + (((uint32_t)k[3])<<16);
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c += k[4] + (((uint32_t)k[5])<<16);
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mix(a,b,c);
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length -= 12;
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k += 6;
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}
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/*----------------------------- handle the last (probably partial) block */
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k8 = (const uint8_t *)k;
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switch(length)
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{
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case 12: c+=k[4]+(((uint32_t)k[5])<<16);
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b+=k[2]+(((uint32_t)k[3])<<16);
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a+=k[0]+(((uint32_t)k[1])<<16);
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break;
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case 11: c+=((uint32_t)k8[10])<<16; /* fall through */
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case 10: c+=k[4];
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b+=k[2]+(((uint32_t)k[3])<<16);
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a+=k[0]+(((uint32_t)k[1])<<16);
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break;
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case 9 : c+=k8[8]; /* fall through */
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case 8 : b+=k[2]+(((uint32_t)k[3])<<16);
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a+=k[0]+(((uint32_t)k[1])<<16);
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break;
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case 7 : b+=((uint32_t)k8[6])<<16; /* fall through */
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case 6 : b+=k[2];
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a+=k[0]+(((uint32_t)k[1])<<16);
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break;
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case 5 : b+=k8[4]; /* fall through */
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case 4 : a+=k[0]+(((uint32_t)k[1])<<16);
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break;
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case 3 : a+=((uint32_t)k8[2])<<16; /* fall through */
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case 2 : a+=k[0];
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break;
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case 1 : a+=k8[0];
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break;
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case 0 : *pc=c; *pb=b; return; /* zero length strings require no mixing */
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}
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} else { /* need to read the key one byte at a time */
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const uint8_t *k = (const uint8_t *)key;
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/*--------------- all but the last block: affect some 32 bits of (a,b,c) */
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|
while (length > 12)
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|
{
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a += k[0];
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a += ((uint32_t)k[1])<<8;
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a += ((uint32_t)k[2])<<16;
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a += ((uint32_t)k[3])<<24;
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b += k[4];
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b += ((uint32_t)k[5])<<8;
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b += ((uint32_t)k[6])<<16;
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b += ((uint32_t)k[7])<<24;
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c += k[8];
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c += ((uint32_t)k[9])<<8;
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c += ((uint32_t)k[10])<<16;
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c += ((uint32_t)k[11])<<24;
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mix(a,b,c);
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length -= 12;
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k += 12;
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}
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/*-------------------------------- last block: affect all 32 bits of (c) */
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switch(length) /* all the case statements fall through */
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|
{
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case 12: c+=((uint32_t)k[11])<<24;
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case 11: c+=((uint32_t)k[10])<<16;
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|
case 10: c+=((uint32_t)k[9])<<8;
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case 9 : c+=k[8];
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case 8 : b+=((uint32_t)k[7])<<24;
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case 7 : b+=((uint32_t)k[6])<<16;
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case 6 : b+=((uint32_t)k[5])<<8;
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case 5 : b+=k[4];
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case 4 : a+=((uint32_t)k[3])<<24;
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case 3 : a+=((uint32_t)k[2])<<16;
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case 2 : a+=((uint32_t)k[1])<<8;
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case 1 : a+=k[0];
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break;
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case 0 : *pc=c; *pb=b; return; /* zero length strings require no mixing */
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}
|
|
}
|
|
|
|
final(a,b,c);
|
|
*pc=c; *pb=b;
|
|
}
|
|
#endif /*SELF_TEST*/
|
|
|
|
|
|
#ifdef WORDS_BIGENDIAN
|
|
/*
|
|
* hashbig():
|
|
* This is the same as hashword() on big-endian machines. It is different
|
|
* from hashlittle() on all machines. hashbig() takes advantage of
|
|
* big-endian byte ordering.
|
|
*/
|
|
static uint32_t
|
|
hashbig( const void *key, size_t length, uint32_t initval)
|
|
{
|
|
uint32_t a,b,c;
|
|
union { const void *ptr; size_t i; } u; /* to cast key to (size_t) happily */
|
|
|
|
/* Set up the internal state */
|
|
a = b = c = 0xdeadbeef + ((uint32_t)length) + initval;
|
|
|
|
u.ptr = key;
|
|
if (HASH_BIG_ENDIAN && ((u.i & 0x3) == 0)) {
|
|
const uint32_t *k = (const uint32_t *)key; /* read 32-bit chunks */
|
|
const uint8_t *k8;
|
|
|
|
/*------ all but last block: aligned reads and affect 32 bits of (a,b,c) */
|
|
while (length > 12)
|
|
{
|
|
a += k[0];
|
|
b += k[1];
|
|
c += k[2];
|
|
mix(a,b,c);
|
|
length -= 12;
|
|
k += 3;
|
|
}
|
|
|
|
/*----------------------------- handle the last (probably partial) block */
|
|
/*
|
|
* "k[2]<<8" actually reads beyond the end of the string, but
|
|
* then shifts out the part it's not allowed to read. Because the
|
|
* string is aligned, the illegal read is in the same word as the
|
|
* rest of the string. Every machine with memory protection I've seen
|
|
* does it on word boundaries, so is OK with this. But VALGRIND will
|
|
* still catch it and complain. The masking trick does make the hash
|
|
* noticeably faster for short strings (like English words).
|
|
*/
|
|
#ifndef VALGRIND
|
|
|
|
switch(length)
|
|
{
|
|
case 12: c+=k[2]; b+=k[1]; a+=k[0]; break;
|
|
case 11: c+=k[2]&0xffffff00; b+=k[1]; a+=k[0]; break;
|
|
case 10: c+=k[2]&0xffff0000; b+=k[1]; a+=k[0]; break;
|
|
case 9 : c+=k[2]&0xff000000; b+=k[1]; a+=k[0]; break;
|
|
case 8 : b+=k[1]; a+=k[0]; break;
|
|
case 7 : b+=k[1]&0xffffff00; a+=k[0]; break;
|
|
case 6 : b+=k[1]&0xffff0000; a+=k[0]; break;
|
|
case 5 : b+=k[1]&0xff000000; a+=k[0]; break;
|
|
case 4 : a+=k[0]; break;
|
|
case 3 : a+=k[0]&0xffffff00; break;
|
|
case 2 : a+=k[0]&0xffff0000; break;
|
|
case 1 : a+=k[0]&0xff000000; break;
|
|
case 0 : return c; /* zero length strings require no mixing */
|
|
}
|
|
|
|
#else /* make valgrind happy */
|
|
|
|
k8 = (const uint8_t *)k;
|
|
switch(length) /* all the case statements fall through */
|
|
{
|
|
case 12: c+=k[2]; b+=k[1]; a+=k[0]; break;
|
|
case 11: c+=((uint32_t)k8[10])<<8; /* fall through */
|
|
case 10: c+=((uint32_t)k8[9])<<16; /* fall through */
|
|
case 9 : c+=((uint32_t)k8[8])<<24; /* fall through */
|
|
case 8 : b+=k[1]; a+=k[0]; break;
|
|
case 7 : b+=((uint32_t)k8[6])<<8; /* fall through */
|
|
case 6 : b+=((uint32_t)k8[5])<<16; /* fall through */
|
|
case 5 : b+=((uint32_t)k8[4])<<24; /* fall through */
|
|
case 4 : a+=k[0]; break;
|
|
case 3 : a+=((uint32_t)k8[2])<<8; /* fall through */
|
|
case 2 : a+=((uint32_t)k8[1])<<16; /* fall through */
|
|
case 1 : a+=((uint32_t)k8[0])<<24; break;
|
|
case 0 : return c;
|
|
}
|
|
|
|
#endif /* !VALGRIND */
|
|
|
|
} else { /* need to read the key one byte at a time */
|
|
const uint8_t *k = (const uint8_t *)key;
|
|
|
|
/*--------------- all but the last block: affect some 32 bits of (a,b,c) */
|
|
while (length > 12)
|
|
{
|
|
a += ((uint32_t)k[0])<<24;
|
|
a += ((uint32_t)k[1])<<16;
|
|
a += ((uint32_t)k[2])<<8;
|
|
a += ((uint32_t)k[3]);
|
|
b += ((uint32_t)k[4])<<24;
|
|
b += ((uint32_t)k[5])<<16;
|
|
b += ((uint32_t)k[6])<<8;
|
|
b += ((uint32_t)k[7]);
|
|
c += ((uint32_t)k[8])<<24;
|
|
c += ((uint32_t)k[9])<<16;
|
|
c += ((uint32_t)k[10])<<8;
|
|
c += ((uint32_t)k[11]);
|
|
mix(a,b,c);
|
|
length -= 12;
|
|
k += 12;
|
|
}
|
|
|
|
/*-------------------------------- last block: affect all 32 bits of (c) */
|
|
switch(length) /* all the case statements fall through */
|
|
{
|
|
case 12: c+=k[11];
|
|
case 11: c+=((uint32_t)k[10])<<8;
|
|
case 10: c+=((uint32_t)k[9])<<16;
|
|
case 9 : c+=((uint32_t)k[8])<<24;
|
|
case 8 : b+=k[7];
|
|
case 7 : b+=((uint32_t)k[6])<<8;
|
|
case 6 : b+=((uint32_t)k[5])<<16;
|
|
case 5 : b+=((uint32_t)k[4])<<24;
|
|
case 4 : a+=k[3];
|
|
case 3 : a+=((uint32_t)k[2])<<8;
|
|
case 2 : a+=((uint32_t)k[1])<<16;
|
|
case 1 : a+=((uint32_t)k[0])<<24;
|
|
break;
|
|
case 0 : return c;
|
|
}
|
|
}
|
|
|
|
final(a,b,c);
|
|
return c;
|
|
}
|
|
#endif /*WORDS_BIGENDIAN*/
|
|
|
|
/*
|
|
-------------------------------------------------------------------------------
|
|
hashlittle() -- hash a variable-length key into a 32-bit value
|
|
k : the key (the unaligned variable-length array of bytes)
|
|
length : the length of the key, counting by bytes
|
|
initval : can be any 4-byte value
|
|
Returns a 32-bit value. Every bit of the key affects every bit of
|
|
the return value. Two keys differing by one or two bits will have
|
|
totally different hash values.
|
|
|
|
The best hash table sizes are powers of 2. There is no need to do
|
|
mod a prime (mod is sooo slow!). If you need less than 32 bits,
|
|
use a bitmask. For example, if you need only 10 bits, do
|
|
h = (h & hashmask(10));
|
|
In which case, the hash table should have hashsize(10) elements.
|
|
|
|
If you are hashing n strings (uint8_t **)k, do it like this:
|
|
for (i=0, h=0; i<n; ++i) h = hashlittle( k[i], len[i], h);
|
|
|
|
By Bob Jenkins, 2006. bob_jenkins@burtleburtle.net. You may use this
|
|
code any way you wish, private, educational, or commercial. It's free.
|
|
|
|
Use for hash table lookup, or anything where one collision in 2^^32 is
|
|
acceptable. Do NOT use for cryptographic purposes.
|
|
-------------------------------------------------------------------------------
|
|
*/
|
|
|
|
static uint32_t
|
|
hashlittle( const void *key, size_t length, uint32_t initval)
|
|
{
|
|
uint32_t a,b,c; /* internal state */
|
|
union { const void *ptr; size_t i; } u; /* needed for Mac Powerbook G4 */
|
|
|
|
/* Set up the internal state */
|
|
a = b = c = 0xdeadbeef + ((uint32_t)length) + initval;
|
|
|
|
u.ptr = key;
|
|
if (HASH_LITTLE_ENDIAN && ((u.i & 0x3) == 0)) {
|
|
const uint32_t *k = (const uint32_t *)key; /* read 32-bit chunks */
|
|
const uint8_t *k8;
|
|
|
|
/*------ all but last block: aligned reads and affect 32 bits of (a,b,c) */
|
|
while (length > 12)
|
|
{
|
|
a += k[0];
|
|
b += k[1];
|
|
c += k[2];
|
|
mix(a,b,c);
|
|
length -= 12;
|
|
k += 3;
|
|
}
|
|
|
|
/*----------------------------- handle the last (probably partial) block */
|
|
/*
|
|
* "k[2]&0xffffff" actually reads beyond the end of the string, but
|
|
* then masks off the part it's not allowed to read. Because the
|
|
* string is aligned, the masked-off tail is in the same word as the
|
|
* rest of the string. Every machine with memory protection I've seen
|
|
* does it on word boundaries, so is OK with this. But VALGRIND will
|
|
* still catch it and complain. The masking trick does make the hash
|
|
* noticeably faster for short strings (like English words).
|
|
*/
|
|
#ifndef VALGRIND
|
|
|
|
switch(length)
|
|
{
|
|
case 12: c+=k[2]; b+=k[1]; a+=k[0]; break;
|
|
case 11: c+=k[2]&0xffffff; b+=k[1]; a+=k[0]; break;
|
|
case 10: c+=k[2]&0xffff; b+=k[1]; a+=k[0]; break;
|
|
case 9 : c+=k[2]&0xff; b+=k[1]; a+=k[0]; break;
|
|
case 8 : b+=k[1]; a+=k[0]; break;
|
|
case 7 : b+=k[1]&0xffffff; a+=k[0]; break;
|
|
case 6 : b+=k[1]&0xffff; a+=k[0]; break;
|
|
case 5 : b+=k[1]&0xff; a+=k[0]; break;
|
|
case 4 : a+=k[0]; break;
|
|
case 3 : a+=k[0]&0xffffff; break;
|
|
case 2 : a+=k[0]&0xffff; break;
|
|
case 1 : a+=k[0]&0xff; break;
|
|
case 0 : return c; /* zero length strings require no mixing */
|
|
}
|
|
|
|
#else /* make valgrind happy */
|
|
|
|
k8 = (const uint8_t *)k;
|
|
switch(length)
|
|
{
|
|
case 12: c+=k[2]; b+=k[1]; a+=k[0]; break;
|
|
case 11: c+=((uint32_t)k8[10])<<16; /* fall through */
|
|
case 10: c+=((uint32_t)k8[9])<<8; /* fall through */
|
|
case 9 : c+=k8[8]; /* fall through */
|
|
case 8 : b+=k[1]; a+=k[0]; break;
|
|
case 7 : b+=((uint32_t)k8[6])<<16; /* fall through */
|
|
case 6 : b+=((uint32_t)k8[5])<<8; /* fall through */
|
|
case 5 : b+=k8[4]; /* fall through */
|
|
case 4 : a+=k[0]; break;
|
|
case 3 : a+=((uint32_t)k8[2])<<16; /* fall through */
|
|
case 2 : a+=((uint32_t)k8[1])<<8; /* fall through */
|
|
case 1 : a+=k8[0]; break;
|
|
case 0 : return c;
|
|
}
|
|
|
|
#endif /* !valgrind */
|
|
|
|
} else if (HASH_LITTLE_ENDIAN && ((u.i & 0x1) == 0)) {
|
|
const uint16_t *k = (const uint16_t *)key; /* read 16-bit chunks */
|
|
const uint8_t *k8;
|
|
|
|
/*--------------- all but last block: aligned reads and different mixing */
|
|
while (length > 12)
|
|
{
|
|
a += k[0] + (((uint32_t)k[1])<<16);
|
|
b += k[2] + (((uint32_t)k[3])<<16);
|
|
c += k[4] + (((uint32_t)k[5])<<16);
|
|
mix(a,b,c);
|
|
length -= 12;
|
|
k += 6;
|
|
}
|
|
|
|
/*----------------------------- handle the last (probably partial) block */
|
|
k8 = (const uint8_t *)k;
|
|
switch(length)
|
|
{
|
|
case 12: c+=k[4]+(((uint32_t)k[5])<<16);
|
|
b+=k[2]+(((uint32_t)k[3])<<16);
|
|
a+=k[0]+(((uint32_t)k[1])<<16);
|
|
break;
|
|
case 11: c+=((uint32_t)k8[10])<<16; /* fall through */
|
|
case 10: c+=k[4];
|
|
b+=k[2]+(((uint32_t)k[3])<<16);
|
|
a+=k[0]+(((uint32_t)k[1])<<16);
|
|
break;
|
|
case 9 : c+=k8[8]; /* fall through */
|
|
case 8 : b+=k[2]+(((uint32_t)k[3])<<16);
|
|
a+=k[0]+(((uint32_t)k[1])<<16);
|
|
break;
|
|
case 7 : b+=((uint32_t)k8[6])<<16; /* fall through */
|
|
case 6 : b+=k[2];
|
|
a+=k[0]+(((uint32_t)k[1])<<16);
|
|
break;
|
|
case 5 : b+=k8[4]; /* fall through */
|
|
case 4 : a+=k[0]+(((uint32_t)k[1])<<16);
|
|
break;
|
|
case 3 : a+=((uint32_t)k8[2])<<16; /* fall through */
|
|
case 2 : a+=k[0];
|
|
break;
|
|
case 1 : a+=k8[0];
|
|
break;
|
|
case 0 : return c; /* zero length requires no mixing */
|
|
}
|
|
|
|
} else { /* need to read the key one byte at a time */
|
|
const uint8_t *k = (const uint8_t *)key;
|
|
|
|
/*--------------- all but the last block: affect some 32 bits of (a,b,c) */
|
|
while (length > 12)
|
|
{
|
|
a += k[0];
|
|
a += ((uint32_t)k[1])<<8;
|
|
a += ((uint32_t)k[2])<<16;
|
|
a += ((uint32_t)k[3])<<24;
|
|
b += k[4];
|
|
b += ((uint32_t)k[5])<<8;
|
|
b += ((uint32_t)k[6])<<16;
|
|
b += ((uint32_t)k[7])<<24;
|
|
c += k[8];
|
|
c += ((uint32_t)k[9])<<8;
|
|
c += ((uint32_t)k[10])<<16;
|
|
c += ((uint32_t)k[11])<<24;
|
|
mix(a,b,c);
|
|
length -= 12;
|
|
k += 12;
|
|
}
|
|
|
|
/*-------------------------------- last block: affect all 32 bits of (c) */
|
|
switch(length) /* all the case statements fall through */
|
|
{
|
|
case 12: c+=((uint32_t)k[11])<<24;
|
|
case 11: c+=((uint32_t)k[10])<<16;
|
|
case 10: c+=((uint32_t)k[9])<<8;
|
|
case 9 : c+=k[8];
|
|
case 8 : b+=((uint32_t)k[7])<<24;
|
|
case 7 : b+=((uint32_t)k[6])<<16;
|
|
case 6 : b+=((uint32_t)k[5])<<8;
|
|
case 5 : b+=k[4];
|
|
case 4 : a+=((uint32_t)k[3])<<24;
|
|
case 3 : a+=((uint32_t)k[2])<<16;
|
|
case 2 : a+=((uint32_t)k[1])<<8;
|
|
case 1 : a+=k[0];
|
|
break;
|
|
case 0 : return c;
|
|
}
|
|
}
|
|
|
|
final(a,b,c);
|
|
return c;
|
|
}
|
|
|
|
|
|
/*
|
|
* hash_fast(key, length, initval)
|
|
* Wrapper that calls either hashlittle or hashbig, depending on endianness.
|
|
*/
|
|
uint32_t
|
|
hash_fast( const void *key, size_t length) {
|
|
#define NC_ARBITRARY_UINT (992099683U)
|
|
#ifndef WORDS_BIGENDIAN
|
|
return hashlittle(key, length, NC_ARBITRARY_UINT);
|
|
#else
|
|
return hashbig(key, length, NC_ARBITRARY_UINT);
|
|
#endif
|
|
}
|
|
|
|
#ifdef SELF_TEST
|
|
/* used for timings */
|
|
void driver1()
|
|
{
|
|
uint8_t buf[256];
|
|
uint32_t i;
|
|
uint32_t h=0;
|
|
time_t a,z;
|
|
|
|
time(&a);
|
|
for (i=0; i<256; ++i) buf[i] = 'x';
|
|
for (i=0; i<1; ++i)
|
|
{
|
|
h = hashlittle(&buf[0],1,h);
|
|
}
|
|
time(&z);
|
|
if (z-a > 0) printf("time %d %.8x\n", z-a, h);
|
|
}
|
|
|
|
/* check that every input bit changes every output bit half the time */
|
|
#define HASHSTATE 1
|
|
#define HASHLEN 1
|
|
#define MAXPAIR 60
|
|
#define MAXLEN 70
|
|
void driver2()
|
|
{
|
|
uint8_t qa[MAXLEN+1], qb[MAXLEN+2], *a = &qa[0], *b = &qb[1];
|
|
uint32_t c[HASHSTATE], d[HASHSTATE], i=0, j=0, k, l, m=0, z;
|
|
uint32_t e[HASHSTATE],f[HASHSTATE],g[HASHSTATE],h[HASHSTATE];
|
|
uint32_t x[HASHSTATE],y[HASHSTATE];
|
|
uint32_t hlen;
|
|
|
|
printf("No more than %d trials should ever be needed \n",MAXPAIR/2);
|
|
for (hlen=0; hlen < MAXLEN; ++hlen)
|
|
{
|
|
z=0;
|
|
for (i=0; i<hlen; ++i) /*----------------------- for each input byte, */
|
|
{
|
|
for (j=0; j<8; ++j) /*------------------------ for each input bit, */
|
|
{
|
|
for (m=1; m<8; ++m) /*------------ for several possible initvals, */
|
|
{
|
|
for (l=0; l<HASHSTATE; ++l)
|
|
e[l]=f[l]=g[l]=h[l]=x[l]=y[l]=~((uint32_t)0);
|
|
|
|
/*---- check that every output bit is affected by that input bit */
|
|
for (k=0; k<MAXPAIR; k+=2)
|
|
{
|
|
uint32_t finished=1;
|
|
/* keys have one bit different */
|
|
for (l=0; l<hlen+1; ++l) {a[l] = b[l] = (uint8_t)0;}
|
|
/* have a and b be two keys differing in only one bit */
|
|
a[i] ^= (k<<j);
|
|
a[i] ^= (k>>(8-j));
|
|
c[0] = hashlittle(a, hlen, m);
|
|
b[i] ^= ((k+1)<<j);
|
|
b[i] ^= ((k+1)>>(8-j));
|
|
d[0] = hashlittle(b, hlen, m);
|
|
/* check every bit is 1, 0, set, and not set at least once */
|
|
for (l=0; l<HASHSTATE; ++l)
|
|
{
|
|
e[l] &= (c[l]^d[l]);
|
|
f[l] &= ~(c[l]^d[l]);
|
|
g[l] &= c[l];
|
|
h[l] &= ~c[l];
|
|
x[l] &= d[l];
|
|
y[l] &= ~d[l];
|
|
if (e[l]|f[l]|g[l]|h[l]|x[l]|y[l]) finished=0;
|
|
}
|
|
if (finished) break;
|
|
}
|
|
if (k>z) z=k;
|
|
if (k==MAXPAIR)
|
|
{
|
|
printf("Some bit didn't change: ");
|
|
printf("%.8x %.8x %.8x %.8x %.8x %.8x ",
|
|
e[0],f[0],g[0],h[0],x[0],y[0]);
|
|
printf("i %d j %d m %d len %d\n", i, j, m, hlen);
|
|
}
|
|
if (z==MAXPAIR) goto done;
|
|
}
|
|
}
|
|
}
|
|
done:
|
|
if (z < MAXPAIR)
|
|
{
|
|
printf("Mix success %2d bytes %2d initvals ",i,m);
|
|
printf("required %d trials\n", z/2);
|
|
}
|
|
}
|
|
printf("\n");
|
|
}
|
|
|
|
/* Check for reading beyond the end of the buffer and alignment problems */
|
|
void driver3()
|
|
{
|
|
uint8_t buf[MAXLEN+20], *b;
|
|
uint32_t len;
|
|
uint8_t q[] = "This is the time for all good men to come to the aid of their country...";
|
|
uint32_t h;
|
|
uint8_t qq[] = "xThis is the time for all good men to come to the aid of their country...";
|
|
uint32_t i;
|
|
uint8_t qqq[] = "xxThis is the time for all good men to come to the aid of their country...";
|
|
uint32_t j;
|
|
uint8_t qqqq[] = "xxxThis is the time for all good men to come to the aid of their country...";
|
|
uint32_t ref,x,y;
|
|
uint8_t *p;
|
|
|
|
printf("Endianness. These lines should all be the same (for values filled in):\n");
|
|
printf("%.8x %.8x %.8x\n",
|
|
hashword((const uint32_t *)q, (sizeof(q)-1)/4, 13),
|
|
hashword((const uint32_t *)q, (sizeof(q)-5)/4, 13),
|
|
hashword((const uint32_t *)q, (sizeof(q)-9)/4, 13));
|
|
p = q;
|
|
printf("%.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x\n",
|
|
hashlittle(p, sizeof(q)-1, 13), hashlittle(p, sizeof(q)-2, 13),
|
|
hashlittle(p, sizeof(q)-3, 13), hashlittle(p, sizeof(q)-4, 13),
|
|
hashlittle(p, sizeof(q)-5, 13), hashlittle(p, sizeof(q)-6, 13),
|
|
hashlittle(p, sizeof(q)-7, 13), hashlittle(p, sizeof(q)-8, 13),
|
|
hashlittle(p, sizeof(q)-9, 13), hashlittle(p, sizeof(q)-10, 13),
|
|
hashlittle(p, sizeof(q)-11, 13), hashlittle(p, sizeof(q)-12, 13));
|
|
p = &qq[1];
|
|
printf("%.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x\n",
|
|
hashlittle(p, sizeof(q)-1, 13), hashlittle(p, sizeof(q)-2, 13),
|
|
hashlittle(p, sizeof(q)-3, 13), hashlittle(p, sizeof(q)-4, 13),
|
|
hashlittle(p, sizeof(q)-5, 13), hashlittle(p, sizeof(q)-6, 13),
|
|
hashlittle(p, sizeof(q)-7, 13), hashlittle(p, sizeof(q)-8, 13),
|
|
hashlittle(p, sizeof(q)-9, 13), hashlittle(p, sizeof(q)-10, 13),
|
|
hashlittle(p, sizeof(q)-11, 13), hashlittle(p, sizeof(q)-12, 13));
|
|
p = &qqq[2];
|
|
printf("%.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x\n",
|
|
hashlittle(p, sizeof(q)-1, 13), hashlittle(p, sizeof(q)-2, 13),
|
|
hashlittle(p, sizeof(q)-3, 13), hashlittle(p, sizeof(q)-4, 13),
|
|
hashlittle(p, sizeof(q)-5, 13), hashlittle(p, sizeof(q)-6, 13),
|
|
hashlittle(p, sizeof(q)-7, 13), hashlittle(p, sizeof(q)-8, 13),
|
|
hashlittle(p, sizeof(q)-9, 13), hashlittle(p, sizeof(q)-10, 13),
|
|
hashlittle(p, sizeof(q)-11, 13), hashlittle(p, sizeof(q)-12, 13));
|
|
p = &qqqq[3];
|
|
printf("%.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x\n",
|
|
hashlittle(p, sizeof(q)-1, 13), hashlittle(p, sizeof(q)-2, 13),
|
|
hashlittle(p, sizeof(q)-3, 13), hashlittle(p, sizeof(q)-4, 13),
|
|
hashlittle(p, sizeof(q)-5, 13), hashlittle(p, sizeof(q)-6, 13),
|
|
hashlittle(p, sizeof(q)-7, 13), hashlittle(p, sizeof(q)-8, 13),
|
|
hashlittle(p, sizeof(q)-9, 13), hashlittle(p, sizeof(q)-10, 13),
|
|
hashlittle(p, sizeof(q)-11, 13), hashlittle(p, sizeof(q)-12, 13));
|
|
printf("\n");
|
|
|
|
/* check that hashlittle2 and hashlittle produce the same results */
|
|
i=47; j=0;
|
|
hashlittle2(q, sizeof(q), &i, &j);
|
|
if (hashlittle(q, sizeof(q), 47) != i)
|
|
printf("hashlittle2 and hashlittle mismatch\n");
|
|
|
|
/* check that hashword2 and hashword produce the same results */
|
|
len = 0xdeadbeef;
|
|
i=47, j=0;
|
|
hashword2(&len, 1, &i, &j);
|
|
if (hashword(&len, 1, 47) != i)
|
|
printf("hashword2 and hashword mismatch %x %x\n",
|
|
i, hashword(&len, 1, 47));
|
|
|
|
/* check hashlittle doesn't read before or after the ends of the string */
|
|
for (h=0, b=buf+1; h<8; ++h, ++b)
|
|
{
|
|
for (i=0; i<MAXLEN; ++i)
|
|
{
|
|
len = i;
|
|
for (j=0; j<i; ++j) *(b+j)=0;
|
|
|
|
/* these should all be equal */
|
|
ref = hashlittle(b, len, (uint32_t)1);
|
|
*(b+i)=(uint8_t)~0;
|
|
*(b-1)=(uint8_t)~0;
|
|
x = hashlittle(b, len, (uint32_t)1);
|
|
y = hashlittle(b, len, (uint32_t)1);
|
|
if ((ref != x) || (ref != y))
|
|
{
|
|
printf("alignment error: %.8x %.8x %.8x %d %d\n",ref,x,y,
|
|
h, i);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/* check for problems with nulls */
|
|
void driver4()
|
|
{
|
|
uint8_t buf[1];
|
|
uint32_t h,i,state[HASHSTATE];
|
|
|
|
|
|
buf[0] = ~0;
|
|
for (i=0; i<HASHSTATE; ++i) state[i] = 1;
|
|
printf("These should all be different\n");
|
|
for (i=0, h=0; i<8; ++i)
|
|
{
|
|
h = hashlittle(buf, 0, h);
|
|
printf("%2ld 0-byte strings, hash is %.8x\n", i, h);
|
|
}
|
|
}
|
|
|
|
void driver5()
|
|
{
|
|
uint32_t b,c;
|
|
b=0, c=0, hashlittle2("", 0, &c, &b);
|
|
printf("hash is %.8lx %.8lx\n", c, b); /* deadbeef deadbeef */
|
|
b=0xdeadbeef, c=0, hashlittle2("", 0, &c, &b);
|
|
printf("hash is %.8lx %.8lx\n", c, b); /* bd5b7dde deadbeef */
|
|
b=0xdeadbeef, c=0xdeadbeef, hashlittle2("", 0, &c, &b);
|
|
printf("hash is %.8lx %.8lx\n", c, b); /* 9c093ccd bd5b7dde */
|
|
b=0, c=0, hashlittle2("Four score and seven years ago", 30, &c, &b);
|
|
printf("hash is %.8lx %.8lx\n", c, b); /* 17770551 ce7226e6 */
|
|
b=1, c=0, hashlittle2("Four score and seven years ago", 30, &c, &b);
|
|
printf("hash is %.8lx %.8lx\n", c, b); /* e3607cae bd371de4 */
|
|
b=0, c=1, hashlittle2("Four score and seven years ago", 30, &c, &b);
|
|
printf("hash is %.8lx %.8lx\n", c, b); /* cd628161 6cbea4b3 */
|
|
c = hashlittle("Four score and seven years ago", 30, 0);
|
|
printf("hash is %.8lx\n", c); /* 17770551 */
|
|
c = hashlittle("Four score and seven years ago", 30, 1);
|
|
printf("hash is %.8lx\n", c); /* cd628161 */
|
|
}
|
|
|
|
|
|
int main()
|
|
{
|
|
driver1(); /* test that the key is hashed: used for timings */
|
|
driver2(); /* test that whole key is hashed thoroughly */
|
|
driver3(); /* test that nothing but the key is hashed */
|
|
driver4(); /* test hashing multiple buffers (all buffers are null) */
|
|
driver5(); /* test the hash against known vectors */
|
|
return 1;
|
|
}
|
|
|
|
#endif /* SELF_TEST */
|